If you want to plant flowers inside your planter, you cannot use hot glue to adhere your glass marbles. The marbles will fall off due to moisture. You can use silicone rubber sealant or Epoxy glue would also work just as well. This takes about 24 hours to cure, but after that, your ‘jewels’ will stay on regardless of moisture.

Now if you’re not going to plant your blooms directly into the pot, and you are simply using the pot as a decorative cachepot, then you can use hot glue, and the glass marbles will stick very well. But just remember to water your plant away from your jeweled planter, and don’t get it wet !